The definition of "socialism" is pretty slippery. Socialism used to be the broad rubrick of a movement, one of whose branches was communism, one of whose branches was Bolshevism. Broadly speaking, 100 years ago, socialism meant that the workers own the "means of production."
If you look at Europe today, many people refer to the state of affairs as "socialism" (in Europe they call it "social democracy" and its advocates are "social democrats.") In reality, it is welfare capitalism. These are free market systems with government social safety nets. This is true in the United States and in Europe. The only difference is our social safety nets are not quite as wide, most especially in the single area of healthcare. Wherever the dividing line is where you cross over from welfare capitalism to actual socialism, as the term used to be defined, is anyone's guess, but neither Europe nor the US are over that line. In order to define either as socialism, you have to adhere to a broader and more modern definition.
When liberals say they have a positive view of socialism, they are associating it with social welfare programs because conservatives are associating it with social welfare programs. Whenever any social welfare policy is being discussed, conservatives say "that's socialism," wanting people to associate it with communism and all the cold war baggage that entails. In turn, the definition of socialism has been effectively broadened by usage, and liberals will then look at a given social welfare program that they support and think, "if that is socialism, then I support socialism."
- wolf